The process of blending (also known as compositing or image compositing) a subpicture with a destination image typically requires up-sampling the destination image to either the 4:2:2 format or the 4:4:4 format and alpha-blending the subpicture. Video decoders have usually performed this operation in the display or overlay hardware in interleaved 4:2:2 format at video refresh rates (such as 75-85 Hz). While providing excellent results and quality, this approach is costly in terms of gates and also requires significantly more memory bandwidth. This is due to the up-sampling to 4:2:2 or 4:4:4 and performing the operation at the higher display rate. This is especially problematic in the highly price-competitive personal computer (PC) market.
Therefore, there is a need for a less expensive technique for performing subpicture blending.